The cerebral peduncle is made of a mass of nerve fibers, and there is one peduncle on each side of the brain. The term "cerebral" means it is related to the brain. A "peduncle" is a stem-like connector.
The cerebral peduncles are connected to the pons, which is a part of the frontal brain stem that looks like a swelling. Many other nerve bundles also connect to the pons. Cerebral peduncles help transport nerve impulses from the higher part of the brain (cortex) and the brain stem, or lower part of the brain, to other areas of the central nervous system.
The cerebral peduncles help refine our movements. If body movement impulses came straight from the cortex, the movements would seem erratic and clumsy. The peduncles adjust the commands by taking into account where the body parts currently are located before directing the movement, and they sometimes slow down the movement. When there is an injury to cerebral peduncles, the symptoms of the injury show up in the part of the body related to the injured peduncle.